Illinois Natural History Survey - University of Illinois

Little blue heron
Egretta caerulea

 

Taxonomy
Occurence in Illinois
Status
Habitat associations
Guilds
Food-habits
Environmental associations
Life history
Management practices
References


TAXONOMY

 

  • Phylum: Chordata
  • Class: Aves
  • Order: Ciconiiformes
  • Family: Ardeidae
  • Genus: Egretta
  • Species: Egretta caerulea
  • Authority: Linnaeus

Comments on taxonomy:
Tribe: Ardeini. Other names:blue crane, little blue crane, little white crane (immature), levee walker (in Louisiana) *04*.

 


OCCURENCE IN ILLINOIS

The little blue heron is commonly seen periodically in Illinois but does not maintain a large breeding population *01,02,03*. Most recent breeding records:1980, 100 pairs at Pontoon Beach Colony, Madison Co.; 1981, 200-250 nests at Pontoon Beach Colony, Madison Co.; 1982, 250 nests at Pontoon Beach Colony, Madison Co. *23*.

 


STATUS

Items in bold indicate applicable categories
Forest Service Categories: S = recommended for regional sensitive status, F = forest listed species, M = management indicator species

Federal Status:

Endangered Threatened Proposed for listing
Candidate for proposal Recovery plan approved Recovery plan received (USFWS)
Recovery plan in preparation Under notice of review Delisted
Migratory EPA indicator Forest Serv.- Shawnee species (F)

State Status:

Endangered Threatened Proposed

Other:

Game Furbearer Nongame protected
Sportfish Commercial Pest None of the above

Comments on status:
Appeared on state endangered list 1977 and still satisfies requirements of list placement. As wetlands were drained the little blue heron suffered a precipitous decline in population size, has low population numbers, and their habitat is threatened *01*.

 


HABITAT ASSOCIATIONS

Items in bold indicate applicable categories

General habitat:

Unknown Terrestrial Aquatic Riparian

USFS timber inventory forest size class:

Unknown Unstocked Seedling Sapling
Seedling/sapling Pole Mature Over mature

Land use and land cover:

Unknown   Urban Residential
Commercial
Industrial
Transportation, communication
Complex industrial/commercial
Mixed
Other
Agricultural Crop, pasture
Orchards, groves, nurseries
Feedlot
Other
Rangeland Herbaceous
Shrub and brush
Mixed
Forestland Deciduous
Evergreen
Mixed
Water Stream
Lake
Reservoir

Bay
Wetland Forest
Non-forest
Barren Salt flat
Beach
Sand
Rock
Mine
Transit
Mix

 


Forest cover types:

Cover typeStructural stageCanopy closureSeason
Oak-gum-cypress Young tree
(1-9" dia.)
Unknown Spring/summer
Oak-gum-cypress Mature
(9" dia. & 100 yrs. old)
Unknown Spring/summer
Elm-ash-cottonwood Young tree
(1-9" dia.)
Unknown Spring/summer
Elm-ash-cottonwood Mature
(9" dia. & 100 yrs. old)
Unknown Spring/summer

Associated tree species:

  • Cottonwood
  • Black willow
  • Sand-bar willow

National wetland inventory classifications:

SystemSubsystemClassSubclassWater regime modifiersWater chemistry
Lacustrine Littoral Emergent vegetation Persistent Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Emergent vegetation Nonpersistent Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Flat Mud Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Scrub/shrub Deciduous Intermittently exposed/permanent nontidal Freshwater
Palustrine Emergent vegetation Persistent   Intermittently exposed/permanent nontidal Freshwater
Palustrine Emergent vegetation Nonpersistent   Intermittently exposed/permanent nontidal Freshwater
Palustrine Flat Mud   Intermittently exposed/permanent nontidal Freshwater
Palustrine Forest Deciduous   Intermittently exposed/permanent nontidal Freshwater
Palustrine Scrub/shrub Deciduous   Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Emergent vegetation Persistent Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Emergent vegetation Nonpersistent Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Flat Mud Intermittently exposed/permanent nontidal Freshwater

Comments on species-habitat associations:
Little blue herons seem to prefer freshwater and are found in lakes ponds, marshes, sloughs, marshy shores of streams & coastal estuaries *01,02,04,05*. Also known to frequent rice fields. Little blue herons nest in a variety of trees, most often hardwoods. Throughout the literature these plant species are common: buttonbush, willow sp., phragmites, and cottonwoods. Small fishes are a principal food item.

Important plant and animal association: Little blue herons are most often associated with other heron species such as snowy egret and tricolored heron *01*.

High value habitats

HabitatStructural stageSeason
Water Special habitat Spring
Water Special habitat Summer
Wetland Special habitat Spring
Wetland Special habitat Summer
Marsh Special habitat Spring
Marsh Special habitat Summer
Swamp Special habitat Spring
Swamp Special habitat Summer
Shrub swamp Special habitat Spring
Shrub swamp Special habitat Summer
Lakes and ponds Special habitat Summer/fall
Reservoir Special habitat Summer/fall
Streams Special habitat Summer/fall
Marsh restoration Special habitat Summer/fall

Species-habitat interrelations: The little blue heron is found primarily in freshwater marshes, also lakes, ponds, sloughs and marshy stream borders. Shallow waters, sometimes mudflats are principle foraging grounds, though in their absence dry fields may be used. Nesting occurs in dense thickety growth forms that border wetlands, usually hardwoods. Foraging grounds appear to be most essential and optimal nesting habitat may be sacrificed.

 


GUILDS

Feed-guilding:

HabitatStructural stageSeasonFeed-guilds
Wetland All Spring Water bottom-unconsolidated bottom, invertebrates other than zooplankton or arthropods
Water bottom-unconsolidated bottom, fish
Water bottom-unconsolidated bottom, amphibians
Water bottom-unconsolidated bottom, reptiles
Water bottom-aquatic bed, invertebrates other than zooplankton or arthropods
Water bottom-aquatic bed, fish
Water bottom-aquatic bed, amphibians
Water bottom-aquatic bed, reptiles
Water column- invertebrates other than zooplankton or arthropods
Water column- fish
Water column- amphibians
Water column- reptiles
Water column- birds
Water surface- invertebrates other than zooplankton or arthropods
Water surface- fish
Water surface- amphibians
Water surface- reptiles
Water surface- birds
Wetland All Spring Terrestrial surface- arthropods
Terrestrial surface- invertebrates other than arthropods
Terrestrial surface- amphibians
Terrestrial surface- reptiles
Terrestrial surface- birds
Wetland All Summer Water bottom-unconsolidated bottom, invertebrates other than zooplankton or arthropods
Water bottom-unconsolidated bottom, fish
Water bottom-unconsolidated bottom, amphibians
Water bottom-unconsolidated bottom, reptiles
Water bottom-aquatic bed, invertebrates other than zooplankton or arthropods
Water bottom-aquatic bed, fish
Water bottom-aquatic bed, amphibians
Water bottom-aquatic bed, reptiles
Water column- invertebrates other than zooplankton or arthropods
Water column- fish
Water column- amphibians
Water column- reptiles
Water column- birds
Water surface- invertebrates other than zooplankton or arthropods
Water surface- fish
Water surface- amphibians
Water surface- reptiles
Water surface- birds
Wetland All Summer Terrestrial surface- arthropods
Terrestrial surface- invertebrates other than arthropods
Terrestrial surface- amphibians
Terrestrial surface- reptiles
Terrestrial surface- birds

Comments on feed-guilding:
The little blue heron feeds primarily in shallow waters of lagoons, swamps, marshes, & also rice fields & mudflats. Most important food items are small fishes and crayfishes *01,03*. If marshes or swamps dry up, the little blue heron has been known to survive solely on insects of grasslands, e.g. grasshoppers, crickets, and beetles *04*.

Breed-guilding:

HabitatStructural stageSeasonBreed-Guilds
Wetland Special habitat Spring Shrub strata, canopy of broad-leaved deciduous shrubs
Shrub strata, canopy of needle-leaved deciduous shrubs
Shrub strata, canopy of broad-leaved evergreen shrubs
Shrub strata, canopy of needle-leaved evergreen shrubs
Shrub strata, grass and grasslike vegetation extending into shrub strata
Shrub strata, forb vegetation extending into shrub strata
Wetland Special habitat Summer Shrub strata, canopy of broad-leaved deciduous shrubs
Shrub strata, canopy of needle-leaved deciduous shrubs
Shrub strata, canopy of broad-leaved evergreen shrubs
Shrub strata, canopy of needle-leaved evergreen shrubs
Shrub strata, grass and grasslike vegetation extending into shrub strata
Shrub strata, forb vegetation extending into shrub strata

Comments on breed-guilding:
Little blue herons usually copulate in the nest or close to it *06, 07*. Nests are usually located in low dense thickety growth forms *03*. Little blue herons nest colonially in homogeneous groups often near other heron species *26*.

 


FOOD-HABITS

Trophic level is CARNIVORE

Food itemLife stage/plant part
Invertebrates Unknown
Arthropoda Unknown
Arachnida (spiders, ticks, scorpions, daddy longlegs) See comments
Crustaceans See comments
Malacostraca (isopods, amphipods, crayfishes) See comments
Insecta Unknown
Odonata (dragonflies, damselflies) Unknown
Orthoptera (grasshoppers, crickets, cockroaches) Unknown
Coleoptera (beetles) Unknown
Osteichtyes (bony fishes) See comments
Amphibians Adult
Amphibians Unknown
Salientia (frogs, toads) See comments
Salientia (frogs, toads) Juvenile
Salientia (frogs, toads) Adult
Reptiles See comments
Testudines (turtles) See comments
Sauria (lizards, skinks, iguana) See comments
Serpentes (snakes) See comments
Important:
Malacostraca (isopods, amphipods, crayfishes) See comments
Osteichtyes (bony fishes) See comments
Salientia (frogs, toads) See comments
Juvenile:
Invertebrates Unknown
Arthropoda Unknown
Arachnida (spiders, ticks, scorpions, daddy longlegs) See comments
Crustaceans See comments
Malacostraca (isopods, amphipods, crayfishes) See comments
Insecta Unknown
Odonata (dragonflies, damselflies) Unknown
Orthoptera (grasshoppers, crickets, cockroaches) Unknown
Coleoptera (beetles) Unknown
Osteichtyes (bony fishes) See comments
Amphibians Adult
Amphibians Unknown
Salientia (frogs, toads) Juvenile
Reptiles See comments
Testudines (turtles) See comments
Sauria (lizards, skinks, iguana) See comments
Serpentes (snakes) See comments
Adult:
Invertebrates Unknown
Arthropoda Unknown
Arachnida (spiders, ticks, scorpions, daddy longlegs) See comments
Crustaceans See comments
Malacostraca (isopods, amphipods, crayfishes) See comments
Insecta Unknown
Odonata (dragonflies, damselflies) Unknown
Orthoptera (grasshoppers, crickets, cockroaches) Unknown
Coleoptera (beetles) Unknown
Osteichtyes (bony fishes) See comments
Amphibians Adult
Amphibians Unknown
Salientia (frogs, toads) Juvenile
Reptiles See comments
Testudines (turtles) See comments
Sauria (lizards, skinks, iguana) See comments
Serpentes (snakes) See comments

Comments on food habits: 
General: Little blue herons prey chiefly (and always in Illinois) on freshwater animals. Most important are small fishes, crayfishes, frogs, and aquatic insects, also eaten are turtles, snakes, lizards, other insects, spiders *01,03,04,05,06,07,08,13*.
Juvenile: Juvenile food habits apparently do not differ from adult food habits *20*.
Adult: See general food habits.


ENVIRONMENTAL ASSOCIATIONS

General:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitats: vegetated streambank
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: swamp
  • Aquatic habitats: see comments
  • Aquatic habitats: marsh
  • Aquatic habitats: unknown
  • Vegetation mosaics/edges: see comments
  • Ecotones: see comments
  • Shrubs: see comments
  • Coniferous forest: see comments
  • Hardwood forest: see comments
  • Canopy closure (%) of trees: see comments
  • Ground cover- shrub (%): see comments
  • Human associations: wildlife refuges/sanctuaries
  • Human associations: see comments

Limiting:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: swamp
  • Aquatic habitats: see comments
  • Aquatic habitats: marsh
  • Canopy closure (%) of trees: see comments
  • Ground cover- shrub (%): see comments
  • Human associations: see comments

Feeding juvenile:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: swamp
  • Aquatic habitats: see comments
  • Aquatic habitats: marsh

Resting juvenile:

  • Canopy closure (%) of trees: see comments
  • Ground cover- shrub (%): see comments

Feeding adult:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: swamp
  • Aquatic habitats: see comments
  • Aquatic habitats: marsh

Resting adult:

  • Canopy closure (%) of trees: see comments
  • Ground cover- shrub (%): see comments

Breeding adult:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitats: see comments
  • Canopy closure (%) of trees: see comments
  • Ground cover- shrub (%): see comments
  • Human associations: see comments

Comments on environmental associations:
General: Marshes and swampy areas are essential to the little blue herons occurrence and survival *03*. Though primarily used as foraging sites, border vegetation occurring as dense thickety growth form are preferred and necessary for nesting *03*. Preferred nest sites may suffer for a prime foraging habitat *03*.
Feeding juvenile: Little blue herons must have unpolluted wetlands, as they forage primarily in shallow waters of sloughs, marshes, and swampy areas.
Resting juvenile: Roosts in dense thickets and trees in or near foraging and nesting habitats *05,07*.
Feeding adult: See comments on feeding juvenile.
Resting adult: See comments on resting juvenile.
Breeding adult: Little blue herons breed in wetland situations that provide a good foraging habitat and nesting structure. Preferred areas are undisturbed by human activity *01,03,10,17*.


LIFE HISTORY

Origin: Native *02*.

Physical description: Slender medium sized heron. 25"-29" length; 41" wingspread wt. to 14 oz. Adult:slatey blue-grey, with a deep maroon- brown neck; legs dark. Immature:all white; tips of primaries bluish black. Legs, deep olive. Bill:pale bluish tipped in black. Also seen in transitional "pied" or "calico" stage *03,04,07,22*. No subspecies *07,08*.

Reproduction: No information available on breeding in Illinois *00,03*. Little blue herons arrive on breeding grounds in Arkansas in mid- March *06*. This species breeds farther inland by preference. Males select territories upon arrival and subsequently start to display *07*. Little blue herons nest collonially and are usually associated with other species of herons *03*. Courtship displays occur on nesting territory and usually near eventual nest site *03, 06,07*. The ritualized courtship continues from sunrise to sunset. Males may build nest foundation before acquiring a mate. Copulation commences during initial stages of nest building and continues throughout laying period *07*. A good nest site requires a suitable supply of sticks and support for the nest *07*. The nest may range from a flimsy platform to a sometimes substantially bulky nest and takes approximately 5-6 (3-7) days to build *04,05,6,07*. The male gathers most sticks and gives them to female who does the actual construction *06,07*. Twig transfer is accompanied by an elaborate ceremony *07*. The nest is usually placed low, 5-10 ft, in dense vegetation, to occasionally 40 ft. in a swamp tree *03,04,07*. In Florida and Arkansas nest construction occurs the last week in March or 1st week in April *07*. Eggs are layed:Fla., Dec. 27-June 3, usually April 1-25; La., Apr. 7-May 16; Ark.,late Apr. *03,04,07*. Average clutch size is 4-5 (3-6) pale bluegreen eggs (44.0 X 33.5 Mm) and take approximately 5-8 days to lay with 1 egg layed every other day *06,07*. Little blue herons will replace a clutch that has been destroyed *07*. Both parents incubate for approximately 22-24 days *04,06,07*. Incubation begins with laying of the first egg *03* or the 2nd egg with partial incubation of the first *07*. Relieving ceremonies are similar to that of other heron spp. *05*. At hatching the young are covered with dark brownish grey down with buffy tips on crest *07*. It takes approximately 3-5 days for entire clutch to hatch and in Fla. peak hatching occurs the 2nd week in may *07*. There is apparently 1 brood/yr. *04,08*. Initially, young are fed by regurgitation of food in the nest. At the end of the first week young then grab the bill of their parents to stimulate regurgitation in the usual heron manner *05,06,07*. In Arkansas the total time to rear 4 young from the point of nest construction to their independence is approximately 80 days *06*. Palmer (1962) reports the time span from hatching to fledging is 35-40 days *07*. Wershkul (1979) reports for Miss. and Ala. parental care consists of:brooding (1-10 days); guardian (11-18 days); post-guardian (19-56 days) *12*. Yearling birds will nest but the proportion is not known *03,06*. Little blue herons are reported to breed at 1 year *08,15*. Even though subadult or "white" birds try to mate they constitute <2% of nestings at bird & sunken islands in Fla. *15*. The oldest bird recorded was found dead in Miss., 7 years 4 mos. *04*.

Behavior: Upon arrival (S. Illinois, late March; C. Illinois, early Apr.) Territories are selected and defended by males for hostile and sexual displays, copulation and nest site *07*. The size of the initial territory selected by the male is always greater than the size defended by the pair *07,13*. No quantitative figures are available. Pair formation occurs on the males territory after which a smaller "nesting territory" is defended by both against conspecifics and other nesting herons *07*. The little blue heron exhibits a much less complex courtship ritual than other ardeids. "The stretch" is their principal display (see Rodgers 1978, Palmer 1962) *07,15*. The little blue heron breeds from S. Illinois and New England southward throughout the south Atlantic states and Mississippi River Valley to southern South America *01,05*. Its stay in Illinois is from mid-Apr. to early Sept. which includes few nesting birds and many post-breeding migrants *01,02*. The only current breeding site in Illinois is near St. Clair and Madison Co.'s *02,23* but more may exist *02*. Although a single brood pair-bond is the rule, much promiscuity exists *06,07*. In Arkansas, Meanley (1955) reported that many females were serviced more by foreign males than their own males *06*. Post-breeding dispersal (July-Oct) is very evident in the little blue heron with greatest movement in white immature birds *03,05*. Sightings have occurred in Nova Scotia, Quebec, Ontario, Wisc., Neb., etc. *05*. These erratic journeys may be caused in part by over-crowding on breeding grounds *05*. In the fall large numbers of white birds are seen in north and central Illinois and even in southern Ill. The ratio of one adult to five immatures is greater than would be accounted for by breeding productivity, which probably indicates an influx of young birds from colonies outside of Illinois *03*. There appears to be a periodicity in numbers of little blue herons seen in late summer in Illinois with peaks occurring every 20 years *03*.

Limiting factors: Although not as widely distributed and not as numerous, the little blue heron is still common in the southern states *05*. It has been reported to be expanding its range northward *07*. In Illinois breeding accounts for 1982 listed approximately 250 nests at the Pontoon Beach Colony, Madison Co. (Kleen 1983) and possibly more throughout the Mississippi Valley *23*. In recent years colonies have been lost by flooding (Clarksville) and cutting of trees (Gale & Grand Marais) *03*. Habitat destruction, draining of swamps, marshes and lagoons is a primary limiting factor in all wading bird populations *01,17*. Little blue herons forage mainly in shallow waters therefore the draining of wetlands limits foraging habitat that is probably more essential than optimal nesting habitat *03*. Little blue herons are also susceptible to eggshell thinning by the constant use of some pesticides (DDE, Dieldrin) *18*. Natural enemies of the little blue heron include racoons, crows, and in Fla. the fish crow is a principal cause of mortality *05*. Little blue herons, like most other herons, are disrupted by human activity and disturbance during the nesting season is a critical factor *17*. It has been assumed in heronries of nearly 100% nesting success, a key factor was rookery isolation *06*.

Population parameters: No information for Illinois exists. Since the 1940's for waders in general, populations in coastal zones are stable or increasing but are experiencing a decline in numbers in inland colonies of Fla., S.C., N.C., Va., and Tx. *19*. This implies freshwater inland wetland habitats in much of the southeastern U.S., Which once supported these populations, have been more greatly stressed or reduced in area than coastal wetlands *19*. The little blue heron is no longer the most common heron in these southeastern colonies. It has also been agreed in the northeast that post- breeding invasions of immatures has been greatly reduced since 1950's *19*. In the southeast U.S. The little blue heron shows a considerable flux in numbers of nests from year to year with a slightly downward trend overall. It has been placed (unofficially) as a species of "special concern" in Fla. and Alab. *25*. Hatching success was reported by Rodgers (92.1%), Maxwell & Kale (87%) and Werschkul (82%) *13,10,12*. Clutches were larger among little blue herons nesting in freshwater swamps and smaller in more southerly colonies and may be related to food supply *13*. The greatest cause of egg loss in Fla. was nest collapse (76%) and fish crow predation (10%) *13*. It appears mortality rates are greatest at the nestling stage. Nestling mortality rates increased with each later position in the hatching sequence *12*. The primary reason for this increase was the later chick's inability to compete with nest mates and ultimate starvation *12,13*. Overall nesting success reported; 93% Ark., 100% Fla., 14.5% Ala. *06*. High success may be due to isolation and food abundance *06,10*. Information on survival rates, rate of increase, or sex ratios unavailable.

 


MANAGEMENT PRACTICES

Beneficial:

  • Maintaining natural areas and nature preserves
  • Maintaining unique or special habitat features (wetlands, snags, caves, cliffs, talises, etc.
  • Preserving endangered species habitat
  • Performing field survey prior to prescription
  • Controlling land use and human activities
  • Seasonal restriction of human use of habitats
  • Controlling pollution in aquatic habitats
  • Developing/maintaining lakes and ponds
  • Developing/maintaining wetlands
  • Creating/maintaining wetlands from non-wetlands
  • Developing/maintaining mudflats
  • Protecting existing wetlands
  • Protecting existing wetlands
  • Restoration of wetlands (return flooded or drained areas to previous wetland conditions)
  • Developing/maintaining riparian habitat
  • Developing/maintaining riparian habitat
  • Restricting human disturbance during migration, breeding, and nesting

Adverse:

  • Channelization
  • Dredging
  • Draining ponds/lakes
  • Draining wetlands
  • Strip mining
  • Applying pesticides
  • Clearcutting forests

Comments on management practices:
Habitat preservation is the key factor in the protection of wading birds *17*. The draining of wetlands and constant use of pesticides is a serious threat. Sanctuaries are probably the best means of preserving habitat. Also survey and classify all areas to aid in quick solutions *17*. The little blue heron is protected by the Illinois Endangered Species Act as of 1977 *01*. It is also protected by the Migratory Bird Treaty Act of 1918 *24* & the Ill. Wildlife Code 1971 *27*.

 


REFERENCES

0. KATUSIC, PATTI L. ILL. NAT. HIST. SURV., 607 E. PEABODY DR., CHAMPAIGN, IL. 61820 (217)333-6846.

1. BOWLES, M. 1981. ENDANGERED AND THREATENED VERTEBRATE ANIMALS & VASCULAR PLANTS OF ILLINOIS. ILL. DEPT. OF CONS. P. 35, 189.

2. BOHLEN, H.D. 1978. AN ANNOTATED CHECK-LIST OF THE BIRDS OF ILLINOIS. ILLINOIS STATE MUS., POP. SCI. SER. VOL. IX.

3. GRABER, J., GRABER, R., AND KIRK, E. 1978. ILLINOIS BIRDS: CICONIIFORMES ILL. NAT. HIST. SURV. BIOLOGICAL NOTES NO. 109. P. 25.

4. TERRES, J.K. 1980. THE AUDUBON SOCIETY ENCYCLOPEDIA OF NORTH AMERICAN BIRDS. ALFRED A. KNOPF. NEW YORK. P. 500.

5. BENT, A.C. 1926. LIFE HISTORIES OF NORTH AMERICAN MARSH BIRDS. U.S. NATL. MUS. BULL. NO. 135 PP. 177-185.

6. MEANLEY, B. 1955. A NESTING STUDY OF THE LITTLE BLUE HERON IN EASTERN ARKANSAS. WILS. BULL. 67(2):84-99.

7. PALMER, R.S. 1962. HANDBOOK OF NORTH AMERICAN BIRDS VOL. I. LOONS THROUGH FLAMINGOS. YALE UNIV. PRESS; NEW HAVEN. PP. 428-438.

8. SPRUNT, A. & E.B. CHAMBERLAIN. 1970. SOUTH CAROLINA BIRD LIFE. UNIV. OF SOUTH CAROLINA PRESS, COLUMBIA. P. 87.

9. MENGEL, R.M. 1965. THE BIRDS OF KENTUCKY. ORNITH. MONOGR. NO. 3. P. 163.

10. MAXWELL, G.R. & H.W. KALE. 1977. BREEDING BIOLOGY OF FIVE SPECIES OF HERONS IN COASTAL FLORIDA. AUK 94(4):689-700.

11. PETERSON, C. & LELL, T. 1964. AN UNUSUAL COLONY OF LITTLE BLUE HERONS. WILS. BULL. 77(2):192-193.

12. WERSCHKUL, D.F. 1979. NESTLING MORTALITY AND THE ADAPTIVE SIGNIFICANCE OF EARLY LOCOMOTION IN THE LITTLE BLUE HERON. AUK 96(1):116-130.

13. RODGERS, J.A. 1980. BREEDING ECOLOGY OF THE LITTLE BLUE HERON ON THE WEST COAST OF FLORIDA. CONDOR 82:164-169.

14. MCCRIMMON, D.A. 1978. NEST SITE CHARACTERISTICS AMONG FIVE SPECIES OF HERONS ON THE NORTH CAROLINA COAST. AUK 95:267-280.

15. RODGERS, J.A. 1978. DISPLAY CHARACTERISTICS AND FREQUENCY OF BREEDING BY SUBADULT LITTLE BLUE HERONS. PP. 35-39 IN WADING BIRDS (EDS.) A. SPRUNT, J. OGDEN, & S. WINCKLER. RESEARCH REPORT NO. 7 NATL. AUD. SOC. N.Y.

16. BURGER, J. 1978. THE PATTERN AND MECHANISM OF NESTING IN MIXED- SPECIES HERONRIES. PP. 45-58 IN WADING BIRDS (EDS.) A. SPRUNT, J. OGDEN & S. WINKLER. RES. REP. NO. 7. NATL. AUD. SOC. N.Y.

17. ANDERSON, J.M. 1978. PROTECTION AND MANAGEMENT OF WADING BIRDS. PP. 99-103 IN WADING BIRDS (EDS.) A. SPRUNT, J. OGDEN, & S. WINKLER. RES. RPT. NO. 7. NATL. AUD. SOC. N.Y.

18. BISKUP, M.L., R.W. RISEBROUGH, & J.L. DUSI. 1978. EGGSHELL MEASUREMENTS AND ORGANOCHLORINE RESIDUES IN LITTLE BLUE HERONS. PP. 113-116 IN WADING BIRDS (EDS.) A. SPRUNT, J. OGDEN, & S. WINKLER. RES. RPT. NO. 7. NATL. AUD. SOC. N.Y.

19. OGDEN, J.C. 1978. RECENT POPULATION TRENDS OF COLONIAL WADING BIRDS ON THE ATLANTIC AND GULF COASTAL PLAINES PP. 137-153 IN WADING BIRDS (EDS.) A. SPRUNT, J. OGDEN & S. WINKLER. RES. REPT. NO. 7. NATL. AUD. SOC. N.Y.

20. KUSHLAN, J.A. 1978. FEEDING ECOLOGY OF WADING BIRDS. IN WADING BIRDS (EDS.) A. SPRUNT, J. OGDEN, S. WINKLER. PP. 249-297 RES. REPT. NO. 7. NATL. AUD. SOC. N.Y.

21. 34TH SUPPLEMENT TO THE AMERICAN ORNITHOLOGISTS UNION CHECK-LIST OF NORTH AMERICAN BIRDS. SUPPLEMENT TO AUK VOL. 99(3).

22. PETERSON, R.T. 1980. A FIELD GUIDE TO THE BIRDS. HOUGHTON MIFFLIN CO., BOSTON. P. 100.

23. KLEEN, V. ILLINOIS AUDUBON BULLETIN. ILL. AUD. SOC. 1981 P. 36 1982 P. 24 1983 P. 27.

24. U.S. FISH & WILDLIFE SERV. 1983. CODE OF FEDERAL REGULATION. TITLE 50, WILDLIFE & FISHERIES. CHAP. 1 PP. 11-18. 50 CFR 10.13. LIST OF MIGRATORY BIRDS. SPEC. PUBL. FED. REG. GENERAL SERV. ADMIN. OCT. 1.

25. HAMEL, P., H. LEGRAND, M. LENNARTZ, & S. GAUTHREAUX. 1982. BIRD- HABITAT RELATIONSHIPS ON SOUTHEASTERN FOREST LANDS. U.S.D.A. FOREST SERVICE GEN. TECH. REPORT SE-22. P. 267.

26. HARRISON, H. 1975. A FIELD GUIDE TO BIRDS NESTS. HOUGHTON MIFFLIN CO., BOSTON. 257 PP.

27. ILLINOIS DEPT. CONSERVATION. 1980. CONSERVATION LAWS. CH.61. WILD- LIFE. ART. II. PAR.2.2. REPRINTED FROM ILLINOIS REVISED STATUTES, 1979. WEST PUBL. CO., ST. PAUL, MN. 120 PP.

 


 

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